Friction stir bonding method

ABSTRACT

The present invention aims to provide a friction stir bonding that could restrain occurrence of defects.  
     An end portion of a face plate  11  is abutted against an end portion of a rim material  520 . A segment  525  for overlapping with the rear surface of a face plate  21  is projected from the rim material  520 . The rim material  520  includes a convex portion  523  projecting outwardly therefrom. A friction stir bonding is performed by inserting a rotary tool  50  from the side of the convex portion  523 . The direction of rotation of the rotary tool  50  is rightward when looking from the side of the large-diameter portion  51 . The direction of movement of the rotary tool  50  is from the near side of the paper to the far side of the paper in FIG.  1.  In FIG.  1,  the pressure of fluidized metal is higher at right-hand side of the axial center of the rotary tool  50 . There exists the overlapping surface of the face plate  21  and the projecting segment  525  at the side with high pressure of metal. The convex portion  523  exists at left-hand side of the axial center of the rotary tool  50 . With such configuration, the occurrence of continuous metal oxide or notch at the overlapping surface could be restrained.

FIELD OF THE INVENTION

[0001] The present invention relates to a friction stir bonding method.

DESCRIPTION OF THE RELATED ART

[0002] A friction stir-bonding method is a technique using a round shaft (called a rotary tool) being inserted into the bonding region of members and moving the rotating rotary tool along the junction line, thereby heating, mobilizing and plasticising the bonding region, and realizing a solid-phase bonding of the members. The rotary tool is comprised of a large-diameter portion and the small-diameter portion. The small-diameter portion is inserted into the member to be bonded, and the end surface of the large-diameter portion is in contact with the aforementioned member. A screw is formed to the small-diameter portion.

[0003] Moreover, the friction stir bonding is performed by providing a convex portion to the two members to be bonded on the side for the rotary tool to be inserted, and inserting the small-diameter portion of the rotary tool into the butted region, as well as inserting the large-diameter portion of the rotary tool into the convex portions. The gap between the two members is filled using the metal of the convex portion as the source. The convex portion may be formed only to one of the members. This is used in a case for friction stir bonding members made of extruded materials, at a region where the extruded directions are orthogonalized.

[0004] This technique is disclosed in Japanese Patent Laid-Open Publication No. 11-90655 (U.S. Pat. No. 6,050,474).

SUMMARY OF THE INVENTION

[0005]FIG. 8 is a longitudinal cross-sectional view of a friction stir bonded region at the butted region between a member M1 provided with a convex portion P1 and a member M2 not provided with a convex portion. FIG. 8(A) shows the condition where a rotary tool 50 is inserted into the butted region between the two members M1, M2. FIG. 8(B) is a longitudinal cross-sectional view after bonding, and the hatching indicates the stirred area. The indication of the stirred area is an exemplification. The rotary tool 50 for friction stir-bonding is comprised of a large-diameter portion 51 and a small-diameter portion 52 at the leading end thereof. When performing friction stir bonding, the small-diameter portion 52 is inserted into the butted region, and a part of the large-diameter portion 51 is inserted into the convex portion P1. The leading end of the small-diameter portion 52 is inserted into a projecting segment P2 overlapping the rear surface of the member M2. The lower end of the large-diameter portion 51 is positioned so as to come into contact with the upper surface of the member M2. When bonding is performed, continuous metal oxide A is formed near the surface of the bonded region on the side of the member M2 having no convex portion, as is indicated in FIG. 8(B). It is considered that this metal oxide A is a metal oxide at the surface of the member being enwound and not diffused. Also, the surface overlapped with the projecting segment P2 and the member M2 tends to form a notch B arising towards the upper surface side (large-diameter portion T1 side of the rotary tool T). It is considered that the continuous metal oxide A or the notch B deteriorates strength.

[0006] The object of the present invention is to provide a friction stir bonding method that could restrict occurrence of defects.

[0007] As a result of various examinations, it is considered that the pressure of metal fluidized by the rotation of the rotary tool is not uniform throughout the projected area in the axis direction of the rotary tool, but is different depending on the position. It is considered that the position with high pressure is defined by the direction of rotation and the direction of movement of the rotary tool. It is considered that such leads to occurrence of continuous metal oxide A or notch B.

[0008] The present invention is characterized in placing a member with no convex portion in the position where high pressure is provided, because the position with higher pressure of the fluidized metal is defined by the direction of rotation and direction of movement of the rotary tool.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a longitudinal cross-sectional view of the rim material and the hollow-shaped material of an embodiment of the present invention during bonding;

[0010]FIG. 2 is a plane view of FIG. 1;

[0011]FIG. 3 is a longitudinal cross-sectional view after bonding in FIG. 1;

[0012]FIG. 4 is a front view of the side structure according to one embodiment of the present invention;

[0013]FIG. 5 is a cross-sectional view taken along line V-V in FIG. 4;

[0014]FIG. 6 is a perspective view of a car body of a railway car;

[0015]FIG. 7 is a longitudinal cross-sectional view of the bonded region in another embodiment of the present invention; and

[0016]FIG. 8 is a longitudinal cross-sectional view of the conventional bonded region.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0017] A preferred embodiment of the present invention will now be explained with reference to FIG. 1 through FIG. 6. A car body 500 of a railway car is comprised of a side structure 501 constituting the side surface, a roof structure 502 constituting the roof, an underframe 503 constituting the floor, and an end structure 504 constituting the end portion in the longitudinal direction. The side structure 501, the roof structure 502, and the underframe 503 are respectively formed by bonding plural extruded materials 10, 20. The longitudinal direction (extruded direction) of the extruded materials 10, 20 is positioned toward the longitudinal direction of the car body 500. The extruded materials 10, 20 are hollow-shaped materials made of aluminum alloy.

[0018] The side structure 501 is provided with a plurality of windows 530, and is also provided with an entrance 510 for passengers. A rim material 520 is bonded to the rim of the opening of the entrance 510. The rim material 520 is a thick member having high strength. The rim material 520 is an extruded material made of aluminum alloy, and is bent in a U-shape along the left and right sides and the upper side of the entrance 510.

[0019] The extruded direction of the extruded materials 10, 20 constituting the side structure 501 is in the longitudinal direction of the car body, that is, the side structure 501. Because the rim material 520 is also an extruded material, the extruded direction of the rim material 520 and the extruded direction of the materials 10, 20 are orthogonal at the region of the left and right sides of the entrance 510. The extruded materials 10, 20 are hollow-shaped materials.

[0020] The hollow-shaped material 10 (20) is comprised of two substantially parallel face plates 11 (21), 12 (22), and a plurality of connecting plates 13 (23), 14 (24) connecting the two face plates.

[0021] A connecting plate 14 (24) at the end portion in the width direction of the hollow-shaped material 10 (20) is orthogonal to the face plates 11, 12 (21, 22). To the outer surface side of the connecting portion between the connecting plate 14 and the face plate 11 (12), there is provided a concave portion for the face plate 21 (22) of the hollow material 20 to overlap. The end portions of the hollow-shaped material 10 overlap the face plates 21, 22 of the hollow-shaped material 20. There are provided projecting segments 15 for supporting the face plates 21, 22 to the end portions of the face plates 11, 12. The projecting segment 15 projects from the connecting plate 14. The projecting segment 15 is connected to the concave portion mentioned above.

[0022] To the end portions of the face plates 11, 12 (21, 22), there is provided a convex portion 17 (27) projecting towards the outer surface side (outside in the thickness direction) of the hollow-shaped materials 10, 20. The end surfaces of the face plates 11, 21 and the convex portion 17 (that is, the concave portion at the face plates 11, 12 side) is located at approximately the center of thickness of the connecting plate 14. The end surfaces of the face plate 11 (12) and the convex portion 17 of the hollow-shaped material 10 is abutted against the end surfaces of the face plate 21 (22) and the convex portion 27 of the hollow-shaped material 20.

[0023] The face plate 11 (12) and the face plate 21 (22) constitutes the same plane, and the size of the projection of the convex portions 17, 27 are equal. The width of the two convex portions 17, 27 are equal. The width of the two convex portions is larger than the diameter of the large-diameter portion 51 of the rotary tool 50. The metal of the convex portions 17, 27 becomes the source of metal for filling the gap in the butted region.

[0024] As is shown in FIG. 5, the case of bonding materials 10, 20 will be explained. Before bonding, the two hollow-shaped materials 10, 20 are placed on a pedestal 100, and are fixed thereto. The rotary tool 50 is provided with a small-diameter portion 52 at the leading end of a large-diameter portion 51. The small-diameter portion 52 is provided with a screw. Upon bonding, the rotary tool 50 is inserted into the butted region. The lower end of the large-diameter portion 51 is placed inside the convex portions 17, 27. The small-diameter portion 52 is inserted into the butted region between the face plates 11, 21. The lower end of the small-diameter portion 52 is inserted slightly into the projecting segment 15. The rotating rotary tool 50 is moved along the bonding line of the butted region. The convex portions 17, 27 become the source for filling the gap in the butted region.

[0025] When the friction stir bonding on the upper surface side as is illustrated in FIG. 5 is completed, the hollow-shaped materials 10, 20 are turned upside down, and are performed with friction stir bonding likewise.

[0026] When all of the hollow-shaped materials 10, 20 constituting the side structure 501 is bonded, it is placed with the inner side of the car upward, and unnecessary portions surrounding the openings such as the window 530 or the entrance 510 are taken out by cutting. The end portion of the face plate 21 (11) at the outer side of the car is more projected towards the opening than the end portions of the face plate 22 (12) at the inner side of the car or the connecting plates 23 (24, 13, 14). Next, the side structure 501 processed as is mentioned above is placed on the rim material 520 bent in a U-shape.

[0027] Next, the rim material 520 of the entrance 510 is friction stir bonded to the hollow-shaped material 10, 20. In FIG. 1, the rim material 520 bent in a U-shape is placed to the opening for the entrance 510. The rim material 520 is comprised of a segment 521 for closing the end portions of the hollow-materials 10, 20, a convex portion 523 projecting more outwardly than the outer surface of the face plate 21 (11) at the outer side of the car, a projecting segment 525 overlapping the inner surface of the face plate 21 (11), and the projecting segment 527 overlapping the outer surface of the face plate 22 (12) at the inner side of the car. The end surface at the outer side of the car of the segment 521 excluding the convex portion 523 constitutes a substantially same plane with the outer surface of the face plate 21 (11). The projecting segment 525 at the outer side of the car is in a position concaved from the outer side of the car. The end portion of the face plate 21 (11) is abutted against the rim material 520.

[0028] The butted region is friction stir bonded from above. The rim material 520 is fixed to the pedestal 100. The end portions of the face plates 21, 11 abutted against the rim material 520 is the end portions in the extruded direction, therefore there exists no convex portions 17, 27 on the face plates 11, 21. The hollow-shaped material 10 coming into contact with the central segment 520C of the U-shaped rim material 520 is cut at the end portion in the width direction, therefore no convex portion exists thereon.

[0029] Next, the butted region between the face plate 21 (11) and the rim material 520 is friction stir bonded from above. The small-diameter portion 52 of the rotary tool 50 is inserted into the butted region. The leading end of the small-diameter portion 52 is inserted into the projecting segment 525. A part of the large-diameter portion 51 is inserted into the convex portion 523. The large-diameter portion 51 is inserted so as to form a slight gap between the lower end of the large-diameter portion 51 and the upper surface of the face plate 21 (11). The rotary tool 50 is inserted so as to incline the large-diameter portion 51 side rearward against the direction of movement, therefore it should be carried out so that there exists a gap between the lower most end of the large-diameter portion 51 and the upper surface of the face plate 21 (11).

[0030] After inserting the rotary tool 50 into the region to be bonded as is mentioned above, the rotary tool 50 is rotated and moved along the bonding line. The rotary tool is moved in FIG. 1 from the near side of the paper towards the far side of the paper. In FIG. 2, which is a plane view of FIG. 1, Y represents the direction of movement of the rotary tool 50, and R represents the direction of rotation of the rotary tool 50. The screw of the small-diameter portion 52 is a left-hand screw. When looking at the small-diameter portion 52 side of the rotary tool 50 from the large-diameter portion 51 side, the direction of rotation of the rotary tool 50 is rightwards (clockwise). As is illustrated in FIG. 1, there exists the convex portion 523 to the left-hand side of the axial center of the rotary tool 50, and the projecting segment 525 to the right-hand side thereof, when looking forward from the rotary tool 50 in the direction of movement. The center of rotation of the rotary tool 50 is inclined. The axial center of the large-diameter portion 51 is positioned rearward than the axial center of the small-diameter portion 52, in the direction of movement.

[0031] In FIG. 4, the rotary tool 50 is first inserted into the butted region at the lower end of the right segment 520R of the U-shaped rim material 520, and starts movement therefrom. The rotary tool 50 moves from the right segment 520R towards the center segment 520C, and moves from the center segment 520C to the left segment 520L. Lastly, the rotary tool arrives at the lower end of the left segment 520L, and completes bonding.

[0032] In friction stir bonding, metal of the convex portion 523 is moved to the upper surface side of the face plate 21 (11), and also becomes the source for filling the gap in the butted region between the face plate 21 (11) and the rim material 520.

[0033] After completing the friction stir bonding, the bonded region or the convex portion 523 above the outer surface of the face plate 21 (11) are cut with a grinder. After completing the friction stir bonding, or before completion, the projecting segment 527 and the face plate 22 (12) are fillet welded.

[0034] With such method, the continuous metal oxide A conventionally formed to the vicinity of the upper surface of the bonded region is decreased or eliminated, as is shown in FIG. 3. Also, the notch B formed to the overlapping surface between the projecting segment 525 and the face plate 21 (12) is diminished or eliminated. The hatching in FIG. 3 indicates the stirred region. The stirred region is an exemplification.

[0035] It is considered that the pressure of metal at the bonded region fluidized by the rotary tool 50 is larger at the right-hand side of the axial center of the rotary tool than the left-hand side, in the direction of movement of the rotary tool. It is considered that this results from the non-bonded metal at the front of the rotary tool 50 being shifted to the right-hand side, because the rotary tool 50 is rotated rightwards. It is considered that this is the reason of reducing or eliminating the continuous metal oxide A, even though there exists bonding region with the face plate 21 (11) to the right-hand side of the rotary tool. Moreover, it is considered that this is the reason of the notch B being diminished or eliminated at the overlapping surface, even though there exists overlapping surface to the right-hand side of the rotary tool.

[0036] On the other hand, the pressure on the left-hand side of the rotary tool 50 is lower than the right-hand side. It is considered that this is because there exists no non-bonded metal at the rear side of the rotary tool 50, so that no new metal is supplied to the left-hand side. Therefore, the continuous metal oxide A is reduced or eliminated at the left-hand side. Also, there exists no overlapping surface to the left-hand side.

[0037] In the case where the screw of the small-diameter portion 52 is a right-hand screw, the direction of rotation becomes leftwards (counterclockwise). The high-pressure region in this case is formed to the left-hand side of the axial center, when looking at the direction of movement from the rotary tool 50. Therefore, it is positioned so that the overlapping surface exists on the left-hand side, and the convex portion 527 exists on the right-hand side. That is, the rotary tool 50 is moved from the left segment 520L of the rim material 520 to the right segment 520R via the center segment 520C.

[0038] The embodiment illustrated in FIG. 7 will now be explained. A convex portion 123 is projected at the surface side of an end portion of a plate 111. A projecting segment 125 is projected in parallel to a plate 121 from the leading end of the convex portion 123. A projecting segment 127 is projected in parallel to the projecting segment 125 from the rear surface of the plate 121. A plate 131 is inserted between the two projecting segments 125, 127, and is abutted against the plate 121. The end portion of the face plate 121 is abutted against the end portion of the face plate 111. The lower end of the large-diameter portion 51 of the rotary tool 50 is placed inside the convex portion 123 and the projecting segment 125.

[0039] In the embodiment of FIG. 7, the projecting segments 125, 127 may be eliminated. When the projecting segment 127 is eliminated, it only could restrain occurrence of continuous metal oxide.

[0040] The technical scope of the present invention is not limited to the terms used in the claims or in the summary of the present invention, but is extended to the range in which a person skilled in the art could easily substitute based on the present disclosure.

[0041] The present invention enables performing of friction stir bonding that could restrain occurrence of defects. 

We claim:
 1. A friction stir bonding method, the method comprising the steps of: butting an end portion of a first plate against an end portion of a second plate; projecting a convex portion beyond one surface of said second plate, said convex portion being projected in the thickness direction of said plate from one surface of said butted end portion of said first plate; and performing friction stir bonding using a rotary tool including a small-diameter portion at the leading end of a large-diameter portion, by inserting said small-diameter portion into said butted region; wherein a part of said large-diameter portion is inserted into said convex portion; said rotary tool is rotated rightwards and moved relatively along said butted region, when looking from said large-diameter portion side; said second plate is positioned rightwards from the axial center of said rotary tool, when looking in said direction of movement; and said convex portion is positioned leftwards from the axial center of said rotary tool.
 2. A friction stir bonding method according to claim 1, wherein; the other surface of said end portion of said first plate includes a projecting segment projecting towards said second plate substantially in parallel to said second plate; said projecting segment overlaps the rear surface of said end portion of said second plate, when looking from said large-diameter portion side; and friction stir bonding is performed while a part of the leading end of said small-diameter portion is inserted into said projecting segment.
 3. A friction stir bonding method according to claim 1, wherein: said first plate and said second plate are extruded materials, respectively; an extruded direction of said second extruded material is positioned so as to be substantially orthogonal to an extruded direction of said first extruded material; and friction stir bonding is performed in such state.
 4. A friction stir bonding method, the method comprising the steps of: butting an end portion of a first plate against an end portion of a second plate; projecting a convex portion beyond one surface of said second plate, said convex portion being projected in the thickness direction of said plate from one surface of said butted end portion of said first plate; and performing friction stir bonding using a rotary tool including a small-diameter portion at the leading end of a large-diameter portion, by inserting said small-diameter portion into said butted region; wherein a part of said large-diameter portion is inserted into said convex portion; said rotary tool is rotated leftwards and moved relatively along said butted region, when looking from said large-diameter portion side; said second plate is positioned leftwards from the axial center of said rotary tool, when looking in said direction of movement; and said convex portion is positioned rightwards from the axial center of said rotary tool.
 5. A friction stir bonding method according to claim 4, wherein: the other surface of said end portion of said first plate includes a projecting segment projecting towards said second plate substantially in parallel to said second plate; said projecting segment overlaps the rear surface of said end portion of said second plate, when looking from said large-diameter portion side; and friction stir bonding is performed while a part of the leading end of said small-diameter portion is inserted into said projecting segment.
 6. A friction stir bonding method according to claim 4, wherein: said first plate and said second plate are extruded materials, respectively; an extruded direction of said second extruded material is positioned so as to be substantially orthogonal to an extruded direction of said first extruded material; and friction stir bonding is performed in such state.
 7. A method of producing a railway car, the method comprising the steps of: butting an end portion of a first extruded material against an end portion of a second extruded material; constituting a side structure of a railway car using said first extruded material and said second extruded material as members thereof; constituting a rim of an opening using said first extruded material as a member thereof, said first extruded material including a convex portion projecting to outer side of a car from one surface of said first extruded material, and a projecting segment projecting from the other surface towards said second extruded material substantially in parallel to said second extruded material; overlapping said end portion of said second extruded material to said projecting segment; and friction stir bonding using a rotary tool including a small-diameter portion to the leading end of a large-diameter portion, by inserting said small-diameter portion into said butted region; wherein a part of said large-diameter portion is inserted into said convex portion; said rotary tool is rotated rightwards and moved relatively along said butted region, when looking from said large-diameter portion side; said second extruded material and said projecting segment are positioned rightwards from the axial center of said rotary tool, when looking in said direction of movement; said convex portion is positioned leftwards from the axial center of said rotary tool; and a part of the leading end of said small-diameter portion is inserted into said projecting segment.
 8. A method of producing a railway car according to claim 7, wherein: said rim material is said first extruded material folded so as to possess at least three sides; and said rotary tool is moved from the right side of said rim material to the center side, and to the left side in order of precedence, when looking from outer side of a car.
 9. A method of producing a railway car, the method comprising the steps of: butting an end portion of a first extruded material against an end portion of a second extruded material; constituting a side structure of a railway car using said first extruded material and said second extruded material as members thereof; constituting a rim of an opening using said first extruded material as a member thereof, said first extruded material including a convex portion projecting to outer side of a car from one surface of said first extruded material, and a projecting segment projecting from the other surface towards said second extruded material substantially in parallel to said second extruded material; overlapping a plate of said second extruded material to said projecting segment; and friction stir bonding using a rotary tool including a small-diameter portion to the leading end of a large-diameter portion, by inserting said small-diameter portion into said butted region; wherein a part of said large diameter portion is inserted into said convex portion; said rotary tool is rotated leftwards and moved relatively along said butted region, when looking from said large-diameter portion side; said second extruded material and said projecting segment are positioned leftwards from the axial center of said rotary tool, when looking in said direction of movement; said convex portion is positioned rightwards from the axial center of said rotary tool; and a part of the leading end of said small-diameter portion is inserted into said projecting segment.
 10. A method of producing a railway car according to claim 9, wherein: said rim material is said first extruded material folded so as to possess at least three sides; and said rotary tool is moved from the left side of said rim material to the center side, and to the right side in order of precedence, when looking from outer side of a car. 